The miniaturization of electronic circuits prompted revolutionary advances in many areas of our lives. Some prominent examples range from lap top computers and pocket televisions to global positioning systems and prostheses that provide users with sensory feedback. The advances in electronics have also inspired research and development in the area of orthopedic bone growth stimulation, including the promotion of spinal fusion and healing. This is typically done by implanting electrical current generators in the vicinity of a bone fracture in a patient's body to create a D.C. electric current around the bone fracture. Studies have shown an improved rate of bone growth and fusion when the fractured bone is stimulated in this manner. Other promising stimulation methods include the use of transmitting ultrasound waves through the fracture site.
In addition to bone growth stimulation as outlined above, electronics implanted in the body may also play a role in patient health monitoring. For example, the progress of bone growth may be determined by measuring the amount of electrical resistance of the bone. It is also contemplated that ultrasound imaging is achievable by implanting ultrasound transmitters and receivers at opposed sites and aimed at the locality of interest. A more detailed description of such an ultrasound imaging system may also be found in the above-identified related patent applications.
Conventional methods of implanting electronic circuits, however, give rise to the disadvantage of possible migration of the electrical components, including electronic circuit packages, electrodes and battery packs causing potential shorting of device output. Also, because fracture and fusion sites are mechanically unstable it is common medical practice to provide internal stabilization. Therefore, a need has arisen for apparatus for providing bone growth and fusion stimulation while stabilizing the fractured bone or fusion site. In addition, apparatus for a distributed delivery of the stimulating energy to the injury site is provided.